The Cover (100k JPEG): Cyclic AMP-dependent Protein Kinase The balance between protein kinases and phosphatases plays a key role in regulating many cellular functions. Disturbing this balance can lead to disease or tumor formation. Cyclic AMP-dependent protein kinase (cAPK) was the first kinase to have its 3-D structure solved by X-ray crystallographic methods, and in many ways, cAPK is a paradigm for the entire kinase family. This VRML model from the MICE project highlights the cAPK functional units.